1. Field of the Invention
The present invention relates generally to a wireless charging apparatus and method, and more particularly, to a wireless charging apparatus and method that uses a wireless power receiver to wirelessly receive power from a wireless power transmitter and that charges a battery with the received power.
2. Description of the Related Art
With the continued improvements in the field of Information Technology (IT) and the increasing prevalence of a wide variety of portable electronic products, a variety of techniques have been developed that supply power for portable electronic products. Technology for supplying power typically used a power line in the past. However, wireless power transmission technology, which is capable of wirelessly supplying power, has recently been developed.
Wireless power transmission technology includes technology for delivering electrical energy in the form of electromagnetic waves, electromagnetic induction, or electromagnetic resonance, for example. Wireless power transmission technology makes it possible to supply power wirelessly anytime and anywhere, without the use of power lines, such as, electric wires. This wireless power transmission technology is a core technology for wirelessly charging electronic devices, supplying wireless power for and/or wirelessly charging electric cars, supplying wireless power to remote places, and supplying power to ubiquitous wireless sensors. Thus wireless power transmission technology has attracted the attention of the public as a promising technology to replace the existing schemes of supplying power for and/or charging electronic devices using electric wires.
For example, when wireless power transmission technology is used for a wireless charging apparatus, the wireless charging apparatus may include a wireless power transmitter for supplying power, and a wireless power receiver for receiving power and charging its battery with the received power. The wireless power transmitter may detect when an object is put on a source resonator by measuring a change in load or a change in resonant frequency from a wireless charging standby state. Upon detecting that the object is put on the source resonator, the wireless power transmitter determines whether the object is an object that may undergo wireless charging, or whether the object is just a metallic object, by performing an authentication process, such as, for example, exchanging an IDentifier (ID) with the object. If the authentication is successful, the wireless power transmitter starts negotiations on power transmission, thereby determining that the object put on the source resonator is a wireless rechargeable-charger (e.g., a wireless power receiver). Upon completion of the negotiations, the wireless power transmitter starts supplying wireless power for charging of the wireless power receiver so that the wireless power receiver may be charged. The wireless power transmitter determines whether the wireless power receiver has been fully charged, and stops its power transmission to the wireless power receiver if the wireless power receiver has been fully charged.
In the conventional wireless charging scheme described above, the wireless power transmitter stops its wireless power transmission when the wireless power receiver sends an End Power Transfer (EPT) packet to the wireless power transmitter. Therefore, the wireless power receiver may not perform an auxiliary charge. The term ‘auxiliary charge’, as used herein, may refer to charging that is conducted to supplement the power that has been self-discharged or consumed during use of the wireless power receiver with a full charge status displayed on UI.
Since the conventional wireless charging apparatus cannot perform an auxiliary charge, a User Interface (UI) screen may not display a full charge status with the transmission of wireless power interrupted.
Therefore, although the wireless charging apparatus has performed wireless charging for a long time, the user may misjudge that the wireless charging apparatus is out of order or malfunctions, because the user can not perceive the full charge status on User Interface (UI) screen.
When the battery power of the wireless power receiver drops below a predetermined amount of power due to discharge while in the fully charged state, the wireless power receiver performs recharging instead of the auxiliary charge. During recharging, the wireless power receiver displays a charging status on the UI. Thus, the user may not be able to determine whether the wireless power receiver is performing recharging after being fully charged, or the wireless power receiver is being continuously charged before being fully charged. For example, the user may misjudge that the wireless power receiver is being continuously charged without being fully charged, even though the wireless power receiver is actually being recharged after it was fully charged.